Conventionally, gamma correction is usually applied to a digital video signal inputted into a digital image display apparatus in order to improve display properties to the level of that of Cathode Ray Tube (CRT) apparatus.
However, pseudo contour is caused on the display image when inputting the gamma-corrected video signal into the digital image display apparatus without any treatment, thus resulting in lower display quality.
Therefore, for example, disclosed in Japanese Unexamined Patent Publication Tokukaihei No. 9-185707 (published on Jul. 15, 1997) is technology for reducing the pseudo contour due to the gamma correction. The technology employs signal processing technology in which error diffusion method is applied, in other words, the gamma correction, which is a vital process for a spatial light modulator and a display apparatus with linear luminescence properties, is carried out by random addition of a controlled noise signal into the video signal.
However, in the error diffusion method disclosed in the publication, the noise signal, which is to be added to the video signal, is stored and fed back in order to prevent accumulation of errors. The apparatus is complicated due to the additional need for a memory, which is used for storing the noise signal, and for a circuit to feed back. Consequently, a high cost is a problem.